Pipe carrying hot gases for an internal-combustion engine

ABSTRACT

The fastening of the thin-walled exhaust pipe inside the liquid-cooled covering takes place by means of screws which are distributed in a cross-sectional plane of the exhaust pipe at the circumference. For receiving the screws, brackets are arranged in the wall of the exhaust pipe which have an internal thread corresponding to the screws. In the mounted state, in the area of each bracket, a radially smaller dimensioned space exists between the exhaust pipe and the covering, which smaller space is eliminated after the tightening of the screws. Instead, the pipe is deformed in the cross-sectional plane of the screws in the sections between the brackets. The extent of the deformation depends on the magnitude of the thermal expansion of the pipe to be expected at the operating state, no constraining forces therefore occur at the pipe which endanger the operation and which result from an obstructed thermal expansion.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a pipe carrying hot gases for aninternal-combustion engine which is surrounded with a spacing by aliquid cooled covering and with several brackets arranged at the thinwalled pipe and fastening means interacting with the brackets to fix thepipe at the covering. By means of this type of an arrangement, it isprevented that the hot gas comes in direct contact with theliquid-cooled covering, whereby the influx of heat into the coolant iskept low.

An arrangement of this type of a pipe carrying hot gases is known fromGerman Utility Model (DE-GM) 80 13 256. Several flange-type brackets aredistributed over the length at each longitudinal side of the thin-walledpipe and rest against a corresponding flange surface of theliquid-cooled covering. The fastening of the pipe takes place by meansof screws inserted vertically with respect to the flange face. The hightemperatures of the hot gases, which occur during the operation, resultin considerable thermal expansion differences between the pipe and thecovering, which are compensated only partly by the fastening. Thermalexpansions which cannot be compensated result in constraining forces ofexpansion which result in a stress to the material which cannot becalculated. The effects of the constraining forces of expansion, whenadded to the stress to the internal-combustion engine caused by theoperation, such as vibration and gas pulsation, result in a stressing ofthe pipe which endangers the operation.

It is therefore the object of the invention to provide a pipe forcarrying hot gases for an internal-combustion engine which results in anoperationally safe connection between the pipe and the liquid-cooledcovering.

According to the invention, this object is achieved by providing anarrangement characterized in that the connection of the pipe and thecovering takes place in only one cross-sectional plane, in that at leasttwo brackets are distributed in the cross-sectional plane at thecircumference of the pipe, in that each bracket has a fasteningarrangement radially interacting with a fastening device, and in thatthe pipe, in the mounted state, in the area of each bracket, has aradially smaller dimensioning with respect to the covering, which iseliminated after the effect of the fastening devices. After theinstallation of the pipe into the covering, the wall sections betweenthe brackets are deformed by tensile stress at least in areas on bothsides of the cross-sectional plane of the screws. The deformation is inthe magnitude of the thermal expansion to be expected at the operatingtemperature. The deformation of the pipe generated in the cold state,will decline during the heating, in which case the tensile stress isreduced. In the case of this, as it were, programmed thermal expansionof the pipe, a stressing of the material, that cannot be calculated, bymeans of constraining forces, is avoided. Other developments of theinvention are found in the various claims.

The advantages achieved by means of the invention are mainly that thegenerating of the pipe deformation takes place necessarily with themounting of the fastening devices, that the fastening devices can becontrolled from the outside, that the smaller dimensioning, whichresults in the deformation of the pipe, can be measured clearly duringthe mounting and that a low-cost production of the pipe fastening isobtained.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

FIG. 1 is a partial cross-sectional view of an exhaust gas turbinehaving a pipe carrying hot gases, in the exhaust gas outlet according toLine I--I in FIG. 2;

FIG. 2 is a sectional view of the fastening plane of the pipe accordingto Line II--II in FIG. 1;

FIG. 3 is a cutout of a pipe carrying hot gases with an insertedclamping ring according to Line III--III in FIG. 4;

FIG. 4 is a sectional view of the fastening plane of the pipe accordingto Line IV--IV in FIG. 3;

FIG. 5 is a partial sectional view of an internal-combustion engine witha pipe carrying hot gases in

the exhaust gas outlet of a cylinder according to Line V--V in FIG. 6;

FIG. 6 is a sectional view of the fastening plane of the pipe accordingto Line VI--VI in FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Between an exhaust gas turbine 12 and an exhaust pipe 14, a pipe 11 isarranged which receives the hot exhaust gases of the exhaust gas turbine12 (FIG. 1 and FIG. 2). The thin-walled pipe 11 is surrounded by aliquid-cooled covering 13, to which the pipe 11 and the exhaust pipe 14are fastened. The connection between the pipe 11 and the covering 13takes place at the outlet end 15 of the pipe 11 by means of four screws16, which are arranged radially and in a cross-sectional plane. The wallof the pipe 11, in the cross-sectional plane, corresponding to thecircumferential distribution of the screws 16, is equipped withlentiform brackets 17 which each have a nut thread corresponding to thescrews 16.

In the initial phase of the mounting, when the pipe 11 is pushed intothe covering 13, the pipe 11, in the area of each bracket 17, has aradially smaller dimension. By means of the screws which engage in thenut threads of the brackets 17 and are tightened, the pipe, while itscross-sectional contour is deformed, in the area of each bracket 17, ispulled against the covering. The originally present radially smallerdimensioning will then no longer exist. Instead, the pipe 11, in thecross-sectional plane of the screws 16 in the wall sections between thebrackets 17, is deformed in comparison to the contour shown in FIG. 2 bydrawn-out lines. The radially smaller dimensioning between the brackets17 at the pipe 11 and the covering 13, which causes the deformation isselected such that a deformation occurs which is in the magnitude of thethermal expansion to be expected at the operating temperature of line11. As a result, in the case of the operating temperature of the pipe 11caused by the thermal expansion, a decline takes place of thedeformation generated in the cold state. In the wall sections betweenthe brackets 17, the pipe 11 will then assume the contour shown by adash-dotted line in FIG. 2. An obstruction of the thermal expansioncannot occur. In the warm operating state, the pipe is thereforerelieved from constraining forces which endanger the operation andresult from the obstructed thermal expansion.

An arrangement of the brackets 17, which is irregular in circumferentialdirection, as shown in the embodiment of FIG. 6, improves the vibratingbehavior of the pipe 11. Wall sections of different lengths between thebrackets 17 have different characteristic frequencies so that thevibrations of the pipe which are incited by the pulsating exhaust gasflow, in this manner, cannot build up to a resonant vibration whichendangers the operation.

In FIGS. 3 and 4, a second embodiment is shown of a pipe 11 carrying hotexhaust gases, which refers to the situation shown in FIG. 1 and 2.However, the pipe 11 is constructed to have a smooth wall in thefastening plane and, with respect to the covering 13, in the mountedcondition, has the smaller dimension required for the deformation. Aclamping ring 19 is loosely inserted into the interior of the pipe 11,this clamping ring 19, by means of its radially projecting bracket 17,resting against the interior side of the pipe 11. The fastening of thepipe 11 and the clamping 19 to the covering 13 again takes place bymeans of screws 16, which penetrate the pipe 11 at through-holes and arescrewed into the brackets 17. The pipe 11 and the clamping ring 19, asdescribed above, are deformed after the tightening of the screws 16. Theadvantage of this construction is that the pipe 11 can be constructedwithout any weld seam or with less weld seams. In addition, differentmaterials may be selected for the pipe 11 and the clamping ring 19.

A third embodiment is shown in FIGS. 5 and 6 which shows a pipe 11carrying hot exhaust gases inside a liquid-cooled covering 13 at theexhaust gas outlet of a cylinder of an internal-combustion engine. Thefastening between the pipe 11 and the covering 13 takes place by meansof two screws 16 arranged radially in a cross-sectional plane. Thecross-sectional plane with the screws 16 is arranged approximately inthe center of the longitudinal course of the pipe 11. For receiving thescrews 16, the wall of the pipe 11 is equipped with brackets 17. Asdescribed with respect to the embodiment in FIG. 1 and 2, also in thecase of the second embodiment, in the cold state, a radially smallerdimensioning exists between the pipe 11 in the area of each bracket 17and the covering 13. By means of the tightening of the screws 16, thepipe 11 in the wall sections between the brackets 17 is deformed bymeans of tensile stress. The resulting cross-sectional contour of thepipe 11 between the brackets 17 in the fastening plane of the screws 16corresponds to the representation in FIG. 2 for the cold state and forthe warm operating state.

The brackets 17 are formed by two shoulders 19, 20 which projectradially beyond the outer circumference of the pipe 11 and interact withcorresponding recesses 18 in the covering 13, by means of which the pipe11 is fixed in axial direction.

I claim:
 1. An exhaust pipe for an internal combustion engine, theexhaust pipe having a thin-walled construction, a normal cross-sectionalarea in a cold condition and being gas-tightly surrounded by aliquid-cooled covering which is spaced by a distance from the exhaustpipe; fastening means for elongating the normal cross-sectional area ofthe exhaust pipe and for attaching the exhaust pipe only to the coveringin only one cross-sectional plane; the fastening means being attached tothe exhaust pipe in its cold condition at said cross-sectional plane andbeing operated to pull out the exhaust pipe at that plane to elongatethe cross-sectional area while maintaining the attachment to thecovering.
 2. An exhaust pipe according to claim 1, wherein the fasteningmeans includes fastening point projections attached to the exhaust pipethat extend outwardly therefrom and toward the covering.
 3. An exhaustpipe according to claim 2, wherein the projections are constructed as afixed component of the pipe.
 4. An exhaust pipe according to claim 2,wherein the projections are constructed as a component of a clampingring which can be inserted into the pipe.
 5. An exhaust pipe accordingto claim 4, wherein the fastening means are constructed as screws whichengage in a nut thread in the projections.
 6. An exhaust pipe accordingto claim 1, wherein the exhaust pipe is arranged at an exhaust gasoutlet of a gas turbine.